Devices for regulating electrical discharges



NOV. 24, 1959 w, M R ETAL 2,914,695

7 DEVICES FOR REGULATING ELECTRICAL DISCHARGES Filed April 12, 1957 IN V EN TOR.

ARL W. MEYER JR. EE% GE E. SPAULDING JR.

ATTORNEYS Uni ed States Pa n ,0"

2,914,695 Patented Nov. 24, 1959 REGULATING ELECTRICAL DISCHARGES Earl Meyer, Jr and George E. Spauiding, Jr., Toledo, Ohio, assignors to The Electric Auto-Lite Company,

ToledoyOhio, a corporation of Ghio Application AprillZ, 1957, Serial No. 652,597

l 7 Claims. ci ars-32's DEVICES FOR This invention relates to devices for regulating electricaldischarges and more particularly to the method and means for decreasing and stabilizing the break-down potential required to produce a jump spark across a predetermined space, as well as for producing spark gaps or spark intensifiers adapted to operate consistently for so that spark gaps of the non-sealed type are commer prolonged periods at high sparking rates in excess of.

about 250 sparks per second.

The invention. comprehends a' method for regulating and nsecuring rapid electrical discharges across spaced electrodes at a break-down voltage of low value which is'predictable and consistent.

The invention comprises" means located in predetermined position with respect to spaced electrodes in order to concentrate the established electricalfield to provide a very stable spark gap in which successive electrical disconsistently low voltage; a g g p "The invention contemplates a spark intensifier of extremely stablecharacteristics for operation at high sparkcharges with substantially no time lag are produced at ing' rates in ignition systems of variable speed engines.

The term spark intensifier is herein used to designate a device which is used to provide an auxiliary spark gap in circuit with the firinggap of a spark plug for regulating the electricalfdischargej of the latter until-the firing or secondaryjvoltage of the-ignition system has reached-a potential such as to cause a spark to jump across .the'

auxiliary gap; as well as the gap of the spark plug, al-

though the spark plug may be fouled by carbon deposits or other foreignor deleterious matter.

The invention embraces a non-sealed spark gap for use with electrical ignition systems for internal combustion engines provided with a body having a dielectric constant higherthan airlocate'd in close proximity to the electrodes, 's'os th'at' theestablished electrical field is concen-,

trated to cause a rapid ionization of the air spacebetween theaelectrodes. whereby 3 the non-sealed spark gap discharges consistently at a predeterminedlow break-down voltage-notxgreatly affected variations of atmospheric conditions.

-Theinvention includes a spark gap havingmeans for enhancing the rapid ionization of'the space between the electrodes by -.utilizing"a conducting member separated from the electrodes by a'thin partition having a dielectric constant higherthan air and wherein the conducting member is arranged to bridge the gap between the elec-' trodes 'withouthaving directconnec'tion therewith so as to befin efiect an electrically floating conducting member. According to the foregoing summary of the invention indicating the general nature and substance, its main objective isto provide a device for regulating electrical discharges including means and their arrangement for decreasing and stabilizing the break-down potential required toiproduce 'a jump spark across a predetermined spacewhereby such device is very stable and operates satisfactorily for a long period of time at high sparking rates in excess of about 250 sparks per secondr fionventional spark gaps, as well as spark intensifiers,

cially unavailable. Moreover these problems have not been successfully solved in connection with conventional,

spark gaps or intensifiers of the hermetically sealed type on account of the fact that these devices have undesirable high and inconsistent impulse ratio and surge spark over second.

One of the main objects of the invention is to avoid the foregoing draw-backs and produces a very compact or minute spark gap or'a spark intensifier of extremely stable characteristics and of long-lasting effective life at high sparking rates adapted for use in ignition systems of variable speed high compression multi-cylinder engines. Another object of the invention is to provide a spark gap having dielectric. and electrically floating conducting means whereby the electrical field, due to the application of a voltage to its spaced electrodes, is controlled and concentrated, causing rapid ionization to thereby furnish free electrons radiating into the space separating the electrodes to produce an electrical discharge at a consisent and predictable low voltage producing a simplified spark gap which has a very low impulse ratio and practi I Another object of the present invention is to provide a' spark intensifier which will cause a fouled spark plug to fire at an electrical potential substantially lower than that required heretofore by conventional spark plug intensifiers, which is predictable and consistent, and wherein the stability of the spark intensifier is not impaired when used at the recurrent discharge rate in the high order that is required when the same is used in ignition systems of engines wherein, in actual practice, such rate is in excess of about 250 discharges per second.

Another object of the invention is to provide a spark gap inwhich a conducting metallic band is carried on the outside of a'member including a section of minimum thickness consistent with its insulating strength and which has adielectric constant higher than'air contacting the electrodes and wherein said conducting band is dimensioned to extend the length of the gap separating the electrodes overlapping their firing tips, whereby rapid ionization of the space between the electrodes is consistently attained. 5

. further object of the invention is to provide a spark gap or spark intensifier of the non-sealed type of stable and long-lasting characteristics wherein the'spaced electrodes are interconnected by an insulating spacer or body of high dielectric constant to provide a surface sparking gap and are devoid of sharp points or edges, thus eliminating objectionable electrode pitting which renders conventional devices ineffective after short operating periods.

A further object of the invention is to provide a very point metals, or a of high erosion-resistant conducting. materials without sharp edges; second, a bodyhaving a dielectric constant at least higher than air and of a very thin cross-section consistent with its insulating qualities intervening between the electrodes and in contact .therewith to form, in effect, a surface sparking gap; andithe third and last component, a conducting electricallyfioab] ing member spaced or separated from the electrodes by said dielectric body and dimensioned to over extend or bridge the length of the said surface sparking gap. In

carrying the invention to practice, as shown in the embodiment. herein disclosed, andconsistent with economical manufacture, the dielectricbody constituting the sec-' ond component also performs the function of a housing or mainsupport forthe other components :of the spark Other objects and advantages of this invention relating tothe arrangement, operation and function of the related elements of the structure, to various details of construction, to combinationsof parts and to economies'of m an ufacture, will be apparent to those skilled in theart upon' consideration of the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Referring to the'drawings: I Fig. I is an enlarged isometric view of a sparkgap constructed in accordance with the principles of the present invention; I' V i V Fig. 11 is alongitudinal sectional view, on an enlarged scale, ofthe spark gap shown in Fig. I; a g

I Fig. III is a cross-sectional view, on an enlargedscale, taken in line III-III of the arrows; I Fig. IV is an enlarged longitudinally sectional view of afspark intensifier constructed in accordance with the principles of this invention;

, Fig.-\/T is an enlarged cross-sectional view taken substantially in line V V of Fig; IV looking'in the direction of the arrows.

. The present invention-may be incorporated in any suit able type of device for regulating electrical discharges and, for practical application of its principles,:the same is illustrated in the drawing as embodied in spark gaps and spark intensifiers'of the types highly adaptable'for use in ignition systems of variable speed,, h1gh compression, multi-cylinder engines. However, it is to'be understood that the invention is not limited in its application to the particular forms shown but'that it is contemplated whenever that the principles of the invention may be used the same may be found to be applicable.

Referring to the drawings, and particularly .to Figs. I

to Ill inclusive, the embodiment of the invention therein illustrated, by way of example, shows the dielectric com"- ponent of the spark gap whose dielectric constant is higher than air, performing two functions, first, the means for decreasing and making consistent the break-down potential required to produce a'rapid jump spark across the electrodes, and second, as a, support and housing for the other components of the spark gap. As particularly of Fig. II looking in the direction form the housing from suitable ceramic insulating materials, including porcelain whose dielectric constant is considerably higher than air, so that the housing walls are of a minimum cross-section consistent with its insulating qualities. The housing is dimensioned and arranged to support the electrodes 12 and 13 by direct engagement therewith and maintain them apart in fixed position within its axial bore by having a close fit therewith, so that accurate spacing or a non-conducting gap of predetertions have, at their respective ends, enlarged heads 16 and 17 dimensioned to co-extend' and be in alignment with the outer periphery of the tubular housing 10, forming thereby external terminals or connecting plates 19 and 2t? for the spaced electrodes. The inner end of the respective tubular sections 14- and 15 arecapped by ringlike or annular members 23 and 24 which constitute the other component of'the electrode structure and may be termed as its vulnerable end or discharge surface. The

tubular sections 14 and 15 of the electrodes 12 and 13 are dimensioned to provide a relatively large mass and are preferably made of a base metal or material having good thermal and electrical conductivity not readily oxi-. dizable by electrical discharges. 4

The vulnerable components 23 and 24 of the composite electrodes 12 and 13 are fixed or carried in direct electrical contact with the ends of the corresponding tubular sections 14 and 15 by having their rear surfaces brazed or welded thereto, and are shaped and dimen-' sioned so that their surfaces are in intimate contact with the bore of the housing 10. The annular members 23 and 24 are preferably formed and arranged, so thattheir discharge faces are uniplanar and rounded ed at their outer periphery, as 'at 26 and 27 respectively, thus avoiding sharp edges or square corners adjacent to the surface gap 11, thus providing co-planar flat sec-- tions spaced adjacent to each other in substantially parallel relation and have their ends adjacent to the central bore rounded off as at-28 and 29 respectively.

" The vulnerable sections 23 and 24 of the; composite electrode structures are preferably made of good erosionresistant, conducting materials,or of metals having a" high melting point. I In carrying the invention to practice, it has'been found highly advantageous to form each one of the members 23 and 24 of either tungsten, molybdenum, tantalum, or alloys of such metals. it is contemplated that other materials having'the characteristics before mentioned may be used.

In the form of' the invention disclosed in Figs. I to IH inclusive,'the'means to enhance the rapid ionization ofthe space between the electrodes for decreasing the time lag of the electrical discharge, as well: as regulating and stabilizing'the break-down voltage of the spark gap, are shown in the formof an electrically floating metallic band 31 surrounding or embracingthe electrodes but not physically connected to either. The band 31 in the form shown is coaxial with the electrodes and is separated therefrom by being supported by the housing 10 by having direct engagement with its outer surface 32. The band 31 is preferably made of a homogeneous conducting substance which 'is illustrated in the form of a flat metallic ring surrounding the electrodes and being dimensioned, so that its length is somewhat greater than the length of the space separating the electrodes, so that the outer ends 34'and35 of the band 31 extend beyond a slight distance and thereby overlap a portion However,v

of the ara'of members 23 and 24, as can be seen by aperu'sal; of Fig. H.

The conductingmember31 which, in accordance with theprinciples of the invention in the form shown, depicts the=rmeans toreduce the impulse ratio of the spark gap and makespossiblea fairly low and consistent potential to causeian electrical discharge is symmetrically placed to bridge the surface gap 11 with its outer ends 34 and properly-spaced from the enlarged sections 16 and 17 ."of* :the electrode structure sothat flash-over will not occur'or precede the electrical discharge between the discharge surfaces23 and 24; In carrying the invention into practice, it has beenfound that the space separating'the'outer surfaces 34 and 35 of the conducting bandflwith respect to the'co-adjacent enlarged sections 16 :and' 1.7"of the electrodes should be at least more than one-half of the length of the space separating the discharge surfaces 23 and24, in order to avoid flashovers'therebetween'y .It has been found by experience, basedon comparative tests, that the co-axial separation or fadial spacing of the electrical floating body 31 with respect to the electrodesignificantly affects its function as a controlling factor' in reducing the impulse ratio of the spark'gap and the consistency of its break-down voltage. In view of thisfact, the walls of the housing 10 should be of a minimum cross-section consistent with the strength, as well as the insulating characteristics,

' of'the dielectric material from which thesame is made.

InFigsuIV- and V,. the invention is shown as embodied in a spark intensifier in which the three basic components of the spark gap of s the invention are correlated in a mannervery similar to the device previously described. The spark intensifier shown in Figs. IV and V comprises a'tubular housing 40 of insulating material of high 'dielectricconstant arranged to support electrodes 42 and 43 in spaced relation within its axial bore and 'walls ihaligfiment'thus forming connecting plates or external terminals 49 and 50 for the spark intensifier. The inner ends of the tubular sections 44 and are p'ed 'by hollow cylindrical members 53 and 54 which cfonstituteth'e other components of the electrode structime and are the-vulnerable ends or their discharge faces. The tubular sections 44 and 45 are dimensioned to provide a relatively large mass and are formed of suitable materials having good thermal and electrical conductivity, not readily oxidizable by electrical discharges. The members 53 and 54 are respectively secured to the ends of each one of the sections 44 and 45 by being brazed or welded thereto, and are shaped and dimensioned so thattheirside surfaces are in intimate contact with the inner surface of the housing 40.

The hollow members 53 and 54 have discharge faces of planar configuration rounded off at their outer peripheries, as at 56 and 57 respectively, to avoid sharp edges or square corners adjacent to the surface gap 41, in this manner providing planar flat sections spacedapart in contrasting alignment to provide a non-conducting gap. The hollow members 53 and 54 are preferably rounded ofi at their inner peripheries, as at 58 and 59 respectively, and are made of good erosion-resistant conducting materials, or metals having a high melting point such as tungsten, molybdenum, and tantalum, or alloys of such metals.

' In the spark intensifier of the invention shown in Figs. IV and V, the means provided to enhance the rapid ionization of the space between the electrodes reducing the impulse ratio 'of the non-conducting gap and provide a consistent break-down potential is shown in the form of aconducting plate 61 which partially surrounds the electrodes 42 and 43 in close proximity thereto but not physically connected to either, thus constituting an electrically floating element.

The electrically floating element 61 is shown in Fig. V as a thin cylindrical section, radially spaced from the electrodes by being bonded to the external surface 62 of the housing 40 circumferentially covering or encircling half of its'periphery. The element 61 is symmetrically positioned and dimensioned to provide a length sufficient to bridge the gap separating the electrodes 42 and 43, and extend a slight distance therebeyond for over-lappin 1 their ends, as particularly shown in Fig. IV.

The length of'the dielectric tubular section forming the housing 40 should be correlated with respect to the dimension of the gap 41 and the length of member 61, so

that flash-overs between the conducting member 61 and the electrode terminals 49 and will not occur or precede the jump spark across the discharge surfaces 53 and 54. The conductor body-61 in this form of the invention is preferably produced by spraying or depositing upon the external surface 62 a non-insulating substance to provide a substantially uniform and homogeneous layer of metal or other current-conducting material. Consistent with economical manufacture, it has been found that depositing a layer of silver in solution upon the external surface of thetubular section of the dielectric support 40, and thereafter bonding or fusing the same thereto by the application of heat, produces a very effective electric floating metallic member at low cost in very close proximityto' the electrodes having intimate contact with the dielectric surface 62 of the housing.

Comparative testsindicate that, while maximum effectiveness is obtained by providing the electrical floating member of the invention totally encircling the electrodes, the stability of the gap is not materially impaired when such electrical'fioating member is circumferentially reduced 'to 180 degrees. However, it has been determined that further circumferential reduction tends to decrease its effectiveness and thereby its regulating function as a stabilizing and reduction factor for the break-down voltage of the gap. Moreover, it has been found that reduction of the length of theelectrical floating member has a J tendency to increase the break-down potential for a given gap spacing when such reduction in length does not provide a satisfactory bridging'of the gap. 7 i 9 It should be noted that the actual dimensions of the component elements of theembodiment of the invention herein illustrated have been materially exaggerated in the drawings for sake of clarity, being approximately five times the actual dimensions of the device.

It is to be understood that the above detailed description of the present invention is intended to disclose an embodiment thereof to those skilled in the art, but that the invention is not to be construed as limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of being practiced and carried out in various ways without departing from the spirit of perforated housing {having a dielectric constant "higher than airsupporting said-electrodes inispaced relation and directly contacting the outer surface of theuniplanar discharge faces of the electrodes, and aconducting member electrically floating carried'by the outer wall of said housing and arranged to encircle and bridge the space between the uniplanar discharge faces of the electrodes.

2. A device for making'consistentthe-breakdownpotefltial required to produce an electrical spark across a PT e1 determined space comprising electrodes arranged'apart'to provide a non-conducting gap, 'a spacer having a dielectric constant higher than air intervening between said electrodes and having direct engagement therewith, and a conducting member electrically floating separated from said electrodes by said spacer and being'arranged-to surround and bridge said non-conducting gap and a portion of the electrodes.

3. A spark gap comprising electrodes constructed and arrangedto provide co-planar discharge faces spaced adjacent to each other in substantially parallel relation forming a non-conducting gap, a'tubular cylindrical member having a dielectric constant higher than air directly interconnecting the periphen'esof the discharge faces of the electrodes on the outside of the non-conducting gap, and an electrically floating conducting element encircling the discharge faces of the electrodes and spaced therefrom by said member, said conducting element having a length and being arranged to bridge said non-conducting gap and a portion of the electrodes.

4. A device for making consistent the breakdown potential required to produce an electricspark across a'predetermined space comprising electrodes having'their discharge surfaces spaced apart in-axial alignment to define a predetermined spaced subjected to the atmosphere, a member of insulating material directly contacting the outer surfaces of the electrodes providing a surface'gap across the predetermined spacing of the electrodes, :said insulating member having a relatively high dielectric constant, and a metallic member non-conductivel'y connected to any one of said electrodes whereby the same is electrically floating with respect'thereto, said metallic member contacting the outer wall of said insulating material and having a length dimensioned to bridge said predetermined space.

5. A device for stabilizing the breakdown potential required to produce an electric spark across a predetere mined space comprising two tubular electrodes having uniplanar, discharge surfaces spacedapart in substantially parallel relation to define across a predetermined space on air sparking gap, an open-endedtubular member of insulating material directly contacting the outersurface of the electrodes adjacent their discharge surfaces providing a surface gap across the predeterminedspace separating the electrodes,;said insulatingrriemberhaving airel'a tively high dielectric constant, and a tubular conducting band supported on the outer wall'of said 'tubularmernber in a non-conductive relation to said 'electrodes'whereby said band is electrically floating with respect =thereto,-said band having a length dimensionedto bridgesaid predetermined space and overlap a portion of the-discharge surfaces of each of said electrodes. 7 V

6. A device for making consistent the breakdown potential required to produce an electric, sparkacrossavpredetermined space comprising electrodeshaving their discharge faces spaced apart in 'axialjalignment to define across a predetermined space a spark gap,: each of said electrodes having a central bore whereby, their discharge faces are subjected to the atmosphere, a member 'of insulating material embracing the electrodes by directly contacting-their outer surfaces thereby providing a surface spark gap across the predetermined spaceseparatin'g the discharge faces ofthe electrodes, saidinsulating memher being of very thin cross-section and'having a relatively high dielectric constant, and a-metallic body bonded to the outer surface of said member in a non-conductive relation to said electrodes whereby'said body is electrically floating withfrespect thereto, said'meta-llic body-having a length dimensioned to bridge said surface spark gap and extend therebeyond a slightdistanceto overlap a portion of said electrodes. v

7. A device for stabilizing the breakdownpote'ntial-required to produce an electrical spark across apredetermined space comprising two cylindrical perforated elec-' trodes having planar discharge faces spaced'apart in substantially parallel relation in axial alignment to define across a predetermined space a sparking air gap, :cylindrical housing of insulating material having a relatively high dielectric constant having a central bore embracing the electrodes by directly contacting their outer surfaces, said housing having a very cross-sectionbetweenthe discharge faces of the electrodes providing-thereby a surface spark gap across thespaceseparating their discharge faces, a cylindrical metallic bandbonde'd to fthe outerlwall of said housing, said band having a length dimensioned to bridge said surface spark gap and extend'thercbeyond a slight distance to overlap'a portion of said electrodes without having a direct electrical connectionwith either whereby said metallic band is electrically floating with respectto said electrodes. I

References 'Cited in the file of this-patent UNITED STATES PATE N-"rs 1 PatentNc. 2,914,695 November 24, 1959 Earl Wa Meyer, Jro, et all,

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should readas corrected below.

Column 2 line 24, for produces" read W produce column 7, line 34, for ,spECed read space as.

Signed and sealed this 10th day of May 1960,

(SEAL) Attest:

ROBERT C. WATSON KARL H, AXLINEI Commissioner of Patents Attesting Officer 

